Miami (CNN) -- Hurricane Katia will bring large swells to coastal areas as it passes between Bermuda and the U.S. East Coast overnight, forecasters said.

Katia slipped to a Category 1 storm Wednesday, according to the Miami-based National Hurricane Center.

As of 8 p.m. ET, Katia was about 335 miles (535 kilometers) west-southwest of Bermuda and was spinning to the northwest at 10 mph (17 kph), the hurricane center said.

The storm is expected to make a gradual turn to the north early Thursday, according to the storm's tracking map. The forward speed is expected to increase Thursday night and Friday.

Katia was producing "dangerous surf conditions" along much of the U.S. East Coast and Bermuda on Wednesday, the hurricane center said.

A tropical storm watch remains in effect for Bermuda, with tropical storm conditions possible within 48 hours. Up to 2 inches of rain could fall across Bermuda, and tropical storm-force winds of at least 39 mph are possible through Thursday, especially in gusts, the hurricane center said.

The storm is also expected to cause life-threatening surf and rip current conditions around the island.

Hurricane-force winds of at least 80 mph extended up to 70 miles (110 kilometers) out from the storm's center. Katia's tropical-storm-force winds -- blowing consistently at between 39 and 73 mph -- extended outward up to 205 miles (335 kilometers).

Meanwhile, Tropical Storm Maria formed Wednesday in the Atlantic but posed no immediate threat to land.

As of 5 p.m. ET, Maria was about 1,205 miles (1,935 kilometers) east of the Leeward Islands, forecasters said. It was packing maximum sustained winds of 50 mph (85 kph) and was moving west at 23 mph (37 kph).

Maria is expected to continue its general motion over the next two days, and may strengthen slightly, the hurricane center said.